Auto merge of #96210 - nnethercote:speed-up-TokenCursor, r=petrochenkov

Speed up `TokenCursor`

Plus a few related clean-ups.

r? `@petrochenkov`

Author: bors

Diff for: compiler/rustc_ast/src/tokenstream.rs

@@ -94,16 +94,6 @@ impl TokenTree {
         TokenTree::Token(Token::new(kind, span))
     }
 
-    /// Returns the opening delimiter as a token tree.
-    pub fn open_tt(span: DelimSpan, delim: DelimToken) -> TokenTree {
-        TokenTree::token(token::OpenDelim(delim), span.open)
-    }
-
-    /// Returns the closing delimiter as a token tree.
-    pub fn close_tt(span: DelimSpan, delim: DelimToken) -> TokenTree {
-        TokenTree::token(token::CloseDelim(delim), span.close)
-    }
-
     pub fn uninterpolate(self) -> TokenTree {
         match self {
             TokenTree::Token(token) => TokenTree::Token(token.uninterpolate().into_owned()),
@@ -585,13 +575,20 @@ impl Cursor {
         Cursor { stream, index: 0 }
     }
 
+    #[inline]
     pub fn next_with_spacing(&mut self) -> Option<TreeAndSpacing> {
-        if self.index < self.stream.len() {
+        self.stream.0.get(self.index).map(|tree| {
             self.index += 1;
-            Some(self.stream.0[self.index - 1].clone())
-        } else {
-            None
-        }
+            tree.clone()
+        })
+    }
+
+    #[inline]
+    pub fn next_with_spacing_ref(&mut self) -> Option<&TreeAndSpacing> {
+        self.stream.0.get(self.index).map(|tree| {
+            self.index += 1;
+            tree
+        })
     }
 
     pub fn index(&self) -> usize {

Diff for: compiler/rustc_parse/src/parser/attr_wrapper.rs

@@ -100,21 +100,16 @@ rustc_data_structures::static_assert_size!(LazyTokenStreamImpl, 144);
 
 impl CreateTokenStream for LazyTokenStreamImpl {
     fn create_token_stream(&self) -> AttrAnnotatedTokenStream {
-        // The token produced by the final call to `{,inlined_}next` or
-        // `{,inlined_}next_desugared` was not actually consumed by the
-        // callback. The combination of chaining the initial token and using
-        // `take` produces the desired result - we produce an empty
-        // `TokenStream` if no calls were made, and omit the final token
-        // otherwise.
+        // The token produced by the final call to `{,inlined_}next` was not
+        // actually consumed by the callback. The combination of chaining the
+        // initial token and using `take` produces the desired result - we
+        // produce an empty `TokenStream` if no calls were made, and omit the
+        // final token otherwise.
         let mut cursor_snapshot = self.cursor_snapshot.clone();
         let tokens =
             std::iter::once((FlatToken::Token(self.start_token.0.clone()), self.start_token.1))
                 .chain((0..self.num_calls).map(|_| {
-                    let token = if cursor_snapshot.desugar_doc_comments {
-                        cursor_snapshot.next_desugared()
-                    } else {
-                        cursor_snapshot.next()
-                    };
+                    let token = cursor_snapshot.next(cursor_snapshot.desugar_doc_comments);
                     (FlatToken::Token(token.0), token.1)
                 }))
                 .take(self.num_calls);